This invention relates to safety glass and more particularly to improvements in a laminating process for preparing safety glass.
Safety glass using plasticized polyvinyl butyral sheet (hereinafter "PVB sheet") is very widely used in windows. The PVB sheet is laminated between inner and outer panes of transparent glass and functions to absorb energy, such as caused by a blow from an object, without penetration of the glass thus providing safety to occupants of the surrounding area.
Safety glass is usually formed by subjecting the assembly to elevated temperature and pressure in an autoclave to bond the components. In the autoclave the components are heated in a chamber filled with oil or air to about 120.degree. to 150.degree. C. at a pressure of 10 to 15 kg/cm.sup.2 to soften and fluidize the PVB sheet to cause it to adhere intimately to the glass panes. Needless to say, autoclave bonding processes require great capital investment and labor which add cost to the finished safety glass laminate.
It is also less widely known to prepare safety glass by a process not using an autoclave (hereinafter "no autoclave process(es)"). As used herein, "no autoclave process(es)" means forming a laminate of glass and PVB sheet without using an autoclave environment wherein superatmospheric pressure on the order of about 10 to 15 kg/cm.sup.2 is present to bond the layers. A typical no autoclave process is described in U.S. Pat. No. 3,234,062, issued Feb. 8, 1966.
A continuing need exists in the art to improve industrially valuable no autoclave processes.